Method for continuous production of high molecular weight polycarbonate resin

Abstract

A high molecular weight polycarbonate resin is continuously produced by subjecting an aromatic polycarbonate prepolymer and an aliphatic diol compound to a linking and highly polymerizing reaction. Even an aliphatic diol compound having a comparatively low boiling point can be allowed to efficiently contribute to the linking and highly polymerizing reaction. An aromatic polycarbonate prepolymer is produced by a polycondensation reaction between an aromatic dihydroxy compound and a diester carbonate, adding an aliphatic diol compound having an aliphatic group bonding to a terminal hydroxyl group to obtain a prepolymer mixture, and subjecting the resulting prepolymer mixture to a linking and highly polymerizing reaction under reduced pressure. The aliphatic diol compound is added at a pressure exceeding 200 torr, and the prepolymer mixture is subjected to a linking and highly polymerizing reaction before the terminal hydroxyl group concentration of the aromatic polycarbonate prepolymer in the prepolymer mixture reaches 2000 ppm.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for continuously producing a high molecular weight polycarbonate resin comprising a step for subjecting an aromatic polycarbonate prepolymer and an aliphatic diol compound to a linking and highly polymerizing reaction.BACKGROUND ART[0002]Polycarbonates have recently come to be widely used in numerous fields due to their superior heat resistance, impact resistance and transparency. Numerous studies have previously been conducted on methods for producing these polycarbonates. Among these, polycarbonates derived from 2,2-bis(4-hydroxyphenyl)propane (to be referred to as “bisphenol A”), for example, have been industrialized by both interfacial polymerization and melt polymerization production methods.[0003]According to this interfacial polymerization, polycarbonate is produced from bisphenol A and phosgene, but it requires the use of toxic phosgene. In addition, this method also has problems such as corrosion of equipment by...

AI Technical Summary

Benefits of technology

[0060]Although raw materials are typically reacted after mixing well in polymerization methods of the prior art, since the reaction between an aromatic polycarbonate prepolymer and an aliphatic diol compound proceeds rapidly, if the raw materials are allowed to react after mixing well, reactions resulting in the formation of by-products such as phenol also proceed rapidly in the system, and a cleavage (fragmentation) reaction of the polymer main chain ends up proceeding due to the presence of those by-products. In the case a cleavage (fragmentation) reaction of the prepolymer main chain proceeds due to the presence of by-products, the reaction time of the highly polymerizing step for highly polymerizing must be prolonged, and as a result thereof, the resin is subjected to thermal hysteresis over a long period of time and resin quality tends to decrease.

[0061]In the present invention, as a result of mixing an aliphatic diol compound with an aromatic polycarbonate prepolymer under a specific condition and continuously supplying the resulting prepolymer mixture to a step for linking and highly polymerizing in a step for linking and highly polymerizing between the aromatic polycarbonate prepolymer and the aliphatic diol compound, the linking reaction can be allowed to proceed rapidly while inhibiting a cleavage (fragmentation) reaction attributable to by-products, thereby making it possible to shorten reaction time in the linking and highly polymerizing reaction vessel.

[0062]Namely, by obtaining a prepolymer compound by adding an aliphatic diol compound to an aromatic polycarbonate prepolymer at a pressure exceeding 200 torr, and supplying to a linking and highly polymerizing reaction vessel before the terminal hydroxyl group concentration of the aromatic polycarbonate prepolymer in the prepolymer mixture reaches 2000 ppm, a prepolymer mixture can be obtained without causing a decrease in addition rate (immobilization rate) while inhibiting volatilization even in the case of an aliphatic diol compound having a comparatively low boiling point, and the prepolymer mixture can be supplied to the linking and highly polymerizing reaction vessel without causing a decrease in molecular weight due to a cleavage (fragmentation) reaction.

[0063]In this manner, since the method of the present invention is able to minimize volatilization and eliminate the need for using in excess even in the case of an aliphatic diol compound having a comparatively low boiling point, the method is economically advantageous in the case of continuously producing industrially. In addition, a high molecular weight polycarbonate resin having an adequately high molecular weight, low N value, superior hue and little structural heterogeneity is obtained by an economically superior method. The method of the present invention can preferably use all applicable aliphatic diol compounds as linking agents. Among them, by using an aliphatic diol compound having a comparatively low boiling point that can be expected to be less expensive and available in stable supply in particular, the method of the present invention allows the obtaining of economic superiority and has greater value for industrial use.

Problems solved by technology

In addition, this method also has problems such as corrosion of equipment by chlorine-containing compounds such by-product hydrogen chloride and sodium chloride as well as methylene chloride used in large amounts as a solvent, and difficulty in removing impurities such as sodium chloride as well as residual methylene chloride that have an effect on polymer properties.

Differing from interfacial polymerization, melt polymerization offers advantages such as not using a solvent, but it also has the intrinsic problem of polymer viscosity in the system increasing rapidly as polymerization progresses, thereby making it difficult to efficiently remove by-product aromatic monohydroxy compounds outside the system while also making it difficult to increase the degree of polymerization due to an extreme decrease in the reaction rate.

However, in the methods disclosed in these publications, it is not possible to adequately increase the molecular weight of the resulting polycarbonate.

When highly polymerization is conducted by a method that uses a large amount of catalyst (Patent Document 2, Patent Document 3) or under severe conditions in the manner of applying high shear (Patent Document 1) as previously described, there are considerable detrimental effects on the physical properties of the resin, such as inferior resin hue or the progression of crosslinking reactions.

However, these methods also have problems such as failure to inadequately increase the degree of polymerization or causing decreases in the inherent physical properties of the resulting polycarbonate resin (such as thermal stability, impact resistance or hue).

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